Submitted to: Molecular Plant Microbe Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2006
Publication Date: 9/1/2006
Citation: Giovanini, M.P., Puthoff, D.P., Nemacheck, J.A., Mittapalli, O., Saltzmann, K.D., Ohm, H., Shukle, R.H., Williams, C.E. 2006. Gene-for-gene defense of wheat against the Hessian fly lacks a classical oxidative burst. Molecular Plant Microbe Interactions. 19:1023-1033. Interpretive Summary: Little is known about which genes and mechanisms are important in defending plants against insect pests. The oxidative burst is a mechanism that has been demonstrated to be involved in plant defense against microbes. Because of proposed similarities in the way that wheat recognizes virulent Hessian fly we tested for involvement of the oxidative burst in wheat defense against the Hessian fly. Through analysis of gene expression, we found that wheat genes involved in oxidative burst did not respond to Hessian fly attack. In addition, active oxygen species, such as peroxide, were not detected. Thus, mechanisms other than the oxidative burst must be involved in induced resistance to this insect pest. These results are important for researchers seeking to engineer new mechanisms of resistance. Genes involved in this resistance mechanism could be altered so that the oxidative burst would be induced upon Hessian fly attack, providing an untapped method for killing Hessian fly larvae.
Technical Abstract: Gene-for-gene recognition responses that activate plant defense mechanisms, such as oxidative burst or hypersensitive response, are common during attack by microbial pathogens as well as by some insects pests. Resistant wheat was assayed for the rapid increase in the levels of active oxygen species (AOS), characteristic of an oxidative burst, as an early response to Hessian fly larvae. No correlation was found between Hessian fly larval feeding and accumulation of O2- or H2O2 in wheat tissues. Loss of resistance was not detected after treatments that inhibit NADPH oxidases and thus interrupt the signal pathway that generates an oxidative burst. In addition, Hessian fly larval feeding did not result in increased gene expression of NADPH oxidase, and other genes known to be involved in generating AOS or detoxifying the cellular environment to protect the plant from the damage of oxidative burst. These data suggest that the wheat gene-for-gene recognition of Hessian fly larvae does not activate the oxidative burst component of resistance that is common to many gene-for-gene interactions between plants and other pathogens.